Electrospray Ionization combined with mass spectrometry has evolved as a powerful technique for the analysis of a wide range of compounds of interest to the field of molecular biology. The proposed research aims to combine Electrospray ionization with a mechanical vibration assist. Ultrasonic nebulizers produce a droplet size proportional to the vibrational frequency applied virtually independent of liquid flow rate and the solution chemistries found in most electrospray applications. The droplets produced by this ultrasonic nebulization have a more uniform size distribution than is produced by pneumatic nebulization. Preliminary studies have indicated that by assisting electrospray with ultrasonic mechanical vibration, high conductivity, and high aqueous content solutions can be sprayed with flow rates ranging from below 1 ul/min to well over 100 ul/min. The ultrasonic vibration allows the generation of a selected droplet size independent of solution chemistries and electrospray conditions. Preliminary testing indicates that this assist technique will substantially improve electrospray performance over a wider range of applications, particularly when the Electrospray Ion Source is used as an L/MS interface.